Method of manufacturing long-distance telegraph and telephone cables



Nov. 5, 1929. U sc I 1,734,207

METHOD OF MANUFACTURING LONG DISTANCE, TELEGRAPH, AND TELEPHONE CABLES Filed Jan. 1927 The annealing should Patented Nev. '5, l29

' UNirian t tan? ERNST FISCHER, Oi 'BEBLIN-TEMPELHOF,

ERTWEBKE GESELLSOHAIT MITBESCHRANKTEB EAFTUNG, OF BEBLIN-SIEMENS-' GERMANY, assrenon 'ro srnmnns-scnucx- STADT, GERMANY, A CORPORATION OF GERMANY METHOD OF HANUFACTUBING LON Application filed January 5, 1927, Serial No My invention relates to a method of manufacturing long-distance telegraph and telephone cables in which added inductanceis uniformly distributed along the conductors.

The conductors of such cables are, for the purpose of obtaining a uniformly distributed. inductance or continuous loading, surrounded with a layer of magnetic material of high permeability. After the application of the magnetic material to the conductor, the conductor together with the magnetic material is annealed, because the permeability of the ma 'etic material is considerably increased hy heating it to a high temperature. preferably be carried out at a temperature of more than 1000 C.

This involves, however, certain difiiculties,

because the copper conductor, which is simultaneously subjectedto the annealing process becomes brittle already at about 800 G.

According to myinvention the annealing of the magnetic material applied to the conductor may be efiected at any necessary temperature, by surrounding the conductor prior to the application'of the magnetic material with a layer of a bad conductor of heat. By this layer the conductor is sufiiciently protected against the heat acting upon the magnetic material even at ve high temperatures. Particularly suitable or the heat insulating layer is a material which consists mainly of as estos, such as for example a fabric ofcotton and asbestos. The cotton is burned during the annealing process so that the layer of'asbestos remaining after the annealin can easily be removed due to loosening o the structure of fabric in consequence of the burning of the cotton. It may be advantageous to remove the heat insulating layer after the annealing com letely or partly in order to eliminate the anger of stretching the magnetic material when laying the cable. This removal is considerably facilitated due to' the above mentioned destruction of the cotton by burning. The air space remaining between conductor and the magnetic material after the removal of the asbestos and the cotton ashes may completely or partly be filled up with I an insulating material, in well known manner.

G-DISTANCE TELEGRAPH AND TELEPHONE CABLES 159,204, and in Germany January 5, 1926.

In order that the copper conductor remain as short a time as possible within the reach of thehigh temperatures, it is advisable to shorten the annealing process by blackening the magnetic material before applying it to the fabric. As is well known, a material having a dull or blackened surface, absorbs heat netic material may be heated and annealedin a simple and convenient manner by an electric current passed through the magnetic material instead of carrying out the annealing process in a furnace.

1 In the accompanying drawing, 1 is a copper conductor, which according to my invention is surrounded by a fabric 2 consisting of cotton and asbestos. Upon this fabric is wound a ta 3 of magnetic material. arious'modifications and changes may be made without departing from the spirit and the scope of the invention, and I desire, there'- 1 fore, that only s uch limitations shall be placed thereon as are imposed by.the prior art.

I claim as my invention:

1. Method of manufacturing long distance telegraph and telephone cables loaded over the entire length with heat treated'magnetic material consisting in providingthe cable with a heat insulating layer comprising a mixture of an essential portion of non-"com-' bustible'with combustible material before the magnetic material is applied and in then annealing the applied magnetic material, whereby the combustibltrmaterial of said layer is consumed and the remainder ofthe layer is left in a porous condition.

2. Method of manufacturi telegraph t e e tire ng long distance and telephone cables loaded over le g h with heat treate m gneuc 1W material, consisting in providing the cable with a heat insulating layer comprising a mixture of asbestos and a combustible fabric filler before the magnetic material is applied and in then annealing the applied magnetic material, whereby the combustible filler of said layer is consumed and the remaining asbestos layer is left in a Porous condition.

In testimony whereof afiix my signature.

ERNST FISCHER. 

